Method and apparatus for effecting gas-stabilized electric arc reactions



July 3, 1962 v H. K. ORBACH 3,042,830

METHOD AND APPARATUS FOR EFFECTING GAS-STABILIZED ELECTRIC ARC REACTIONSFiled April 4, 1960 I9- 4, llL "@IIE? 2 2F l y 4 32 3 5/ INVENTOR.

flrraews vs.

United States Patent METHOD AND APPARATUS FOR EFFECTING GAS-STABILIZEDELECTRIC ARC REACTIONS Harry K. Orbach, Whittier, Calif., assignor, bymesne assignments, to MHD Research, Inc., Newport Beach,

Calif., a corporation of California Filed Apr. 4, 1960, Ser. No. 19,628,11 Claims. (Cl. 313-231) 'This invention relates generally toimprovements in gas stabilized electric arcing apparatus of theso-called plasma jet type which operates to arc-ionize a gas and createa high velocity, high temperature gaseous discharge of the gas and othermaterials passed through the arc. Generally such devices have compriseda body containing a cathode and anode spaced to arc-ionize a gas fedinto the body. The impingement of the plasma upon the electrodes hasnecessitated cooling the electrodes, particularly the anode, by methodsgenerally employing a high velocity, high pressure stream of watercontacting the outer surfaces. Upwards of fifty percent of theelectrical energy fed to the arc is removed by the water, andconsequently is wasted.

My general object is to improve the efficiencies of such devices byemploying as an electrode coolant, a portion of the gases to be heatedby the arc, and in this manner conserve essentially all of the inputenergy for heating of the gases fed to the device. Experience has shownthat the present device, employing part of the input gas or gases as theelectrode coolant, will operate for extended periods without othercooling and with no damage to the electrodes beyond the normallyexpected fused spot on the cathode. Efficiency therefore is maximized.

An unexpected result of the invention which can be used to advantage inchemical processing, is that the arc characteristics, i.e. voltage andamperage, are a function of the type of gas passing the cathode and arenot appreciably afiected by the type of gas entering the arc regionthrough the anode. The former will be termed arc gas and the lattercoolant gas. Normally in devices of this general type, where all the gaspasses the cathode, different physical configurations and differentvoltages are needed for different gas compositions, and often severalhundred volts are required to maintain the arc. The present inventionpermits use of many different reactants as coolant gases withoutaltering the equipment or materially affecting the amperage or voltageas established by the arc.

In addition to increased efficiency and flexibility in voltage choice,the invention affords various additional unique factures: Loweroperating temperatures are allowed by using large quantities of coolantgas. This feature may be used to advantage in chemical synthesis in thatoptimum temperatures may be selected for each reaction and composition.These temperatures often fall below the minimum maintainable withexisting arc equipment in which the arc is extinguishable by high gasflows. Gases which are normally corrosive to a tungsten cathode or causedeposits upon it may be used as the coolant gas since the latter doesnot contact the cathode. Solids may be carried into the arc in a nowefficient and symmetrical manner by the coolant gas, for such purposesas direct reduction of ores. Similar advantages apply to use of theapparatus for the spraying of metal or refractory coatings, whichcurrently is a major use for plasma jet-type devices.

Structurally, the invention contemplates an improved assembly comprisinga body forming a chamber containing an electrode, eg the cathode, andcontaining a tubular anode having a gas mixing passage and arc-gap icespacing from the cathode at the inlet end of the passage, means foradmitting gas to the chamber for ionization in the arc, and means forfeeding coolant gas about the anode and for then passing the gas intothat part of the arc region furthest from the cathode.

The invention will be further understood from the following detaileddescription of an illustrative embodiment shown by the accompanyingdrawing, in which:

FIG. 1 is a view showing the apparatus in longitudinal section;

FIG. 2 is a broken cross section on line 2-2 of FIG. 1;

FIG. 3 is a fragmentary view showing a variational form of thegas-cooled electrode, and

FIG. 4 is a cross section on line 4--4 of FIG. 3.

Referring to the drawing, the apparatus is shown to comprise aconductive metal body 10 containing a chamber 11 which accommodates theconventional illustrated electrode 12 which, typically, may be atungsten-tipped copper or brass cathode receiving current in anysuitable or conventional manner, of which conductor 13 leading fromdirect current generator 14 is illustrative. A gas to be ionized is fedto chamber 11 through line 15, and if desired, provision may be made foradmitting to the chamber a second gas through line 16. The chamber isdefined at its inner end by annular projection or shoulder 17 having acentral opening 18 for accommodation of the anode generally indicated at19.

As illustrated in FIGS. 1 and 2, the anode 19, made typically of copper,is generally tubular for the passage of gas therethrough, and has theform of an annularly hollow body 20 including a reduced neck portion 21received within opening 18 and presenting a recessed mouth 22 exposed tothe arc gap at 23 and receiving the ionized gas for passage throughaperture 24 into the anode. The latter has a forward closed end 25 and acentral tubular portion 26 spaced at 27 from the aperture 24 and forminga mixing pass-age 28 through which the heated gases are discharged at291 in a high velocity, high temperature stream or jet. The electrode 19is releasably contained within the body 10 by engagement with a sealring 29 contained within the shoulder recess 30, and against which theelectrode is held by a ring 31 threaded at 32 into the end of the bodyand having a shoulder 33 which supports the end face of the electrode.Rings 35 and 36 seal, respectively, between the electrode and ring 31,and between the latter and body 10. As illustrated, the ring 31 may havea mouth 38 flaring away from the projected gas jet.

One or more coolant gases may be introduced to space 40 surrounding theanode 19, by way of inlets 41 which preferably are positioned to directthe gas tangentially into the space, thereby creating a swirling flow ofthe gas which extends its cooling time of contact with the exterior ofthe anode and can act to maintain entrainment of any solids introducedwith the gas. From space 40 the gas flows through circularly distributedand angularly or tangentially directed apertures 42 in the forward wallof the anode into chamber 43, the gas then reversing its flow in coolingcontact with the electrode surfaces in passing into space 27 to join andbecome directly admixed in passage 28 with the gas from passage 24.Thus, as will be observed, the gas introduced to space 40 effectivelycools the anode in being caused to contact both its external andinternal surface before entering the discharge passage.

FIG. 3 illustrates a variational embodiment of the invention, generallysimilar to the first described form except for modification of the anodeat the arc end, and of the coolant gas-passing apertures. Here the anode45 may be made in sections 46, 47 and 48, the first presenting a mouth49 converging to a central opening 50 which may be somewhat larger inrelation to opening 24 in the head recess 54, and then enters passage 55through its tapered mouth 56.

In this FIG. 3 form, passage 55 is shown to be somewhat larger indiameter than opening 50, an illustrative ratio being about 0.3 to 0.18inch. As before, mixing of the coolant gas with the arc gas occurs inspace 51 at the mouth of passage 55, and within the are being projectedthrough opening 50.

In considering the operation of the devices, an arc gas such as argon orhelium may be fed into chamber 11 through line 15 and subjected to hightemperature ionization within the are created in gap 23 between theelectrode 12 and the rear portion of the electrode 19. The hightemperature ionized gas flowing through aperture 24 into passage 48, isadmixed with the coolant gas that has passed about and through the anodeinto space 27, as previously described. The are itself may be blownthrough opening 24 into space 27 with the inner end of tube 26 acting asthe anode surface. Maximum efiiciency in terms of utilization of theelectrical input energy, is assured since no heat is wasted in electrodecooling but instead is absorbed by the coolant stream and carried intothe ionized gas flow. Energy is further extracted from the are bycausing the coolant gas to contact it at nearly a right angle.

The apparatus may be used for carrying out various chemical reactions astypified below, in any of which one of the reactants may serve as thearc gas since each reaction involves a one relatively inert gas.However, it may also be advantageous in any of these reactions to use aninert gas such as argon or helium at the cathode to limit erosion orvoltage requirements. Possible arc gases are underlined in the followingtypical reactions:

In carrying out the above reactions, the arc gas may be introducedthrough line 15 and another or reactant gas supplied as coolant throughline or lines 41. Alternatively, and particularly where a solid reactantis involved, a suitable arc gas may be introduced through line 14 andthe reactants fed to the cooling zone 40. As a further possibility, onereactant gas may be supplied through lines 41 and a second reactant fedto chamber 11 through line 16.

It will be understood that the drawing is illustrative of a typicalembodiment of the invention, and that various changes and modificationsmay be made without departure from its intended spirit and scope.

I claim:

1. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber, a first electrode within said chamber, a secondtubular electrode in said body having an internal gas mixing passage andare gap spacing from said first electrode beyond the inlet end of saidpassage so that the arc enters the second electrode, means for admittingto said chamber a first gas to be heated in said gap and dischargedthrough said passage,

means for feeding a second coolant gas into a space about said secondelectrode and in contact therewith, and means for passing the preheatedcoolant gas then into the heated gas stream within the arc extent insidethe second electrode.

2. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber, a first electrode within said chamber, a secondtubular electrode in said body having an internal gas mixing passage andarc gap spacing from said first electrode beyond the inlet end of saidpassage so that the arc enters the second electrode, means for admittingto said chamber a first gas to be heated in said gap and dischargedthrough said passage, means for feeding a second coolant gas into aspace about said second electrode and in contact therewith, and meansfor passing the preheated coolant gas then into the heated gas streamwithin the arc extent inside the second electrode and at a location atthe mouth of said mixing passage.

3. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber, a first electrode Within said chamber, a secondtubular electrode in said body having an internal gas mixing passage andare gap spacing from said first electrode beyond the inlet end of saidpassage so that the arc enters the second electrode, means for admittingto said chamber a first gas to be heated in said gap and dischargedthrough said passage, means for feeding a second coolant gas into aspace about said second electrode and in contact therewith, means forpassing the preheated coolant gas then into the heated gas stream withinthe arc extent inside the second electrode, and means for introducing athird gas into said chamber for reaction with one of the other gases.

4. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber, a first electrode within said chamber, a secondtubular electrode in said body having an internal gas mixing passage andare gap spacing from said first electrode beyond the inlet end of saidpassage so that the arc enters the second electrode, means for admittingto said chamber a first gas to be heated in said gap and dischargedthrough said passage, means for feeding a second coolant gas into aspace about said second electrode and in contact therewith, means forpassing the preheated coolant gas then into the heated gas stream withinthe arc extent inside the second electrode and at a location at themouth of said mixing passage and means for introducing a third gas intosaid chamber for reaction with one of the other gases.

5. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber, a first electrode within said chamber, a secondtubular electrode in said body having an internal gas mixing passage andare gap spacing from said first electrode beyond the inlet end of saidpassage so that the arc enters the second electrode, means for admittingto said chamber a first gas to be heated in said gap and dischargedthrough said passage, said second electrode containing an annularchamber surrounding said passage, means for feeding a coolant gas into aspace about the second electrode and thence into said annular chamber,and means for then passing the preheated coolant gas from the annularchamber into the heated gas stream within the arc extent inside thesecond electrode.

6. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber, a first electrode within said chamber, a secondtubular electrode in said body having an internal gas mixing passage andare gap spacing from said first electrode beyond the inlet end of saidpassage so that the arc enters the second electrode, means for admittingto said chamber a first gas to be heated in said gap and dischargedthrough said passage, said second electrode containing an annularchamber surrounding said passage, means for feeding a coolant gas into aspace about the second electrode and thence into said annular chamber,means for then passing the preheated coolant gas from the annularchamber into the heated gas stream within the arc extent inside thesecond electrode, and means for introducing a third gas into the firstmentioned chamber for reaction with one of the other gases.

7. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber and containing an annular shoulder at the inner end ofthe chamber, an electrode within said chamber at one side of saidshoulder, a second tubular electrode within the body at the oppositeside of said shoulder and having an internal gas mixing passage and aregap spacing from said first electrode beyond the inlet end of saidpassage so that the arc enters the second electrode, releasable meansengaging the outer end of said second electrode and holding it againstsaid shoulder, means for admitting to said chamber a first gas to beheated in said gap and discharged through said passage, means forfeeding a second coolant gas into a space about said second electrode,and means for passing the coolant gas then into the heated gas streamwithin the arc extent inside the second electrode.

8. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber and containing an annular shoulder at the inner end ofthe chamber, an electrode within said chamber at one side of saidshoulder, a second tubular electrode within the body at the oppositeside of said shoulder and having an internal gas mixing passage and aregap spacing from said first electrode beyond the inlet end of saidpassage, releasable means engaging the outer end of said secondelectrode and holding it against said shoulder, means for admitting tosaid chamber a first gas to be heated in said gap and discharged throughsaid passage, said second electrode containing an annular chambersurrounding said passage,

means for feeding a coolant gas into a space about the second electrodeand thence into said annular chamber, and means for then passing thecoolant gas from the annular chamber into the heated gas stream withinthe are extent inside the second electrode.

9. Gas ionizing apparatus of the character described, comprising a bodyforming a chamber, a first electrode within said chamber, a secondtubular electrode in said body having a gas mixing passage and are gapspacing from said first electrode beyond the inlet end of said passage,means for admitting to said chamber a first gas to be heated in said gapand discharged through said passage, said second electrode having anapertured end exposed to said are and an annular internal chambersurrounding a central tubular portion spaced from said apertured end andforming said mixing passage, means for introducing a coolant gas into anannular space within the body surrounding said second electrode, the gasthence flowing through apertures in the electrode into said internalchamber and thence into the heated gas stream entering said passage.

10. Apparatus according to claim 9, in which said coolant gas isdirected tangentially into said space and said apertures are circularlydistributed about said internal chamber.

11. Apparatus according to claim 10, in which the coolant gas isdirected tangentially into said annular internal chamber.

Clark Jan. 7, 1958 Gi lruth et al Sept. 2, 1958

